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Adequately analyzing and modeling the extreme rainfall events is of great importance because of the effects that their magnitude and frequency can have on human life, agricultural productivity and economic aspects, among others. A single extreme event may affect several locations, and their spatial dependence has to be appropriately taken into account. Classical geostatistics is a well-developed field for dealing with location referenced data, but it is largely based on Gaussian processes and distributions, that are not appropriate for extremes. In this paper, an exploratory study of the annual maximum of monthly precipitation recorded in the northern area of Portugal from 1941 to 2006 at 32 locations is performed. The aim of this paper is to apply max-stable processes, a natural extension of multivariate extremes to the spatial set-up, to briefly describe the models considered and to estimate the required parameters to simulate prediction maps. [ABSTRACT FROM AUTHOR]

The scarcity of freshwater is a growing concern around the world, especially in the developing world and is increasingly threatening human survival in less affluent parts of the world. In arid and semiarid regions, freshwater resources are imperative for the survival of populations as well as development activities in urban centres. Preceding assessments for potential solutions have underestimated the scarcity of water by failing to capture main trends of precipitation and the extent of drought periods. This paper aims to investigate rainfall trends for the City of Windhoek, Namibia. A century scale is examined by reconstructing historical precipitation records, and future trends are subsequently estimated and interpolated using Ordinary Kriging in ArcGIS 10.3. Kriging responds and handles spatial correlation much better for observed data points. The results show locations that receive high rainfall and potential periods for harvesting rainwater. The findings further show that the periods of high rainfall are shorter, and after each high rainfall stretch, a long period of lower rainfall follows immediately. Each low rainfall period is anticipated to last longer than the previous one. These scenarios are highly significant for urban managers in dryland cities such as Windhoek, as they demonstrate when water would need to be extra sparingly managed. This study highlights the need for better water management strategies, if cities in dry climates are to survive the anticipated future water crises. • The changes in climate has induced a shift of the rain season forwards by at least one and half months. • Extreme events are characterised by intense periods of rainfall separated by longer drought periods within a given month. • The combined spatial and rainfall time series data show that some areas will become progressively drier than others. • The results further show some areas will receive rainfall in shorter time period then previously observed. • Better water management strategies are discussed to ensure timely adaptation to the predicted precipitation trends. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents parameters of the diurnal rainfall cycle for rainfall equal or exceeding 2.5mmh−1 during both the summer and winter halves of the year. It then discusses the impact of various circulation systems on the distribution of the frequency of rainfall occurrence during a 24-hday in the summer half of the year. The results of these investigations contribute to a greater understanding of the atmospheric processes associated with heavy precipitation and may be used to improve the forecasting of the temporal distribution of short-duration convective precipitation. A pattern with a single heavy rainfall maximum was identified. A variety of diurnal patterns of amplitude and time of maximum rainfall emerged depending on the atmospheric circulation determining the thermal and humidity properties of air masses. The paper was based on hourly rainfall records in Kraków and on a daily catalogue of atmospheric circulation types in southern Poland spanning the period 1886–2007. [Copyright &y& Elsevier]

Abstract: This paper presents a climatological validation of atmospheric circulation type catalogues included in the COST 733 dataset (COST733CAT). The circulation type classifications ability to describe patterns of the Norwegian precipitation climate is analysed. For all 73 classifications included in the COST733CAT several statistical measures are calculated for each individual circulation type. These statistics include both frequencies of precipitation occurrence and statistical moments used to fit γ-distributions for each circulation type at precipitation stations. In this paper results from four stations in different precipitation regions and classifications with ∼9 types are emphasized. The circulation types employed represent the COST 733 domain 02 (57–72°N, 6°W–25°E). Precipitation occurrence frequency statistics and probability density functions are used to analyse if the types within the circulation type classifications can describe different precipitation conditions. Simple measures are developed in order to compare classifications. The similarity of probability density functions of type specific precipitation within classifications are analysed applying Kolmogorov–Smirnov tests. The type-specific distribution functions are also compared with the probability function of all precipitation events. The results reveal that some classifications, particularly those associated with the neural network methods does not discriminate precipitation distributions very well. On the other side many classifications performs well and get high scores. Evaluating all 73 catalogues the results indicate best results for classifications with 27–30 types. [Copyright &y& Elsevier]

Abstract: Precipitation is one of the most important elements of the hydrological cycle, and extreme events associated with precipitation are considered a key factor in several types of human activities, including agriculture, for instance. Therefore, the main objective of this paper is to evaluate extreme precipitation indices for the past century, and to analyse the possible tendency of future precipitation conditions for this century for the Carpathian Basin. Several climate extreme indices have been analysed according to the guidelines suggested by the joint WMO-CCl/CLIVAR Working Group (formed at the end of the 1990s) on climate change detection. These precipitation indices include the number of wet days using several threshold values, e.g., 20mm (RR20), 10mm (RR10), 5mm (RR5), 1mm (RR1), 0.1mm (RR0.1), the upper quartile and the 95th percentile of daily precipitation in the base-period 1961–1990 (R75 and R95); the maximum number of consecutive dry days (CDD); the highest 1-day precipitation amount (Rx1); the greatest 5-day rainfall total (Rx5); the annual fraction due to extreme precipitation events (R95T); simple daily intensity index (SDII), etc. Our results suggest that regional intensity and frequency of extreme precipitation increased in the Carpathian Basin during the second half of the 20th century, while the total precipitation decreased and the mean climate became slightly drier during the whole 20th century. In the second part of this paper, several IPCC emission scenarios have been compared and GCM outputs have been analysed in order to project precipitation conditions in the Carpathian Basin for the 21st century. These climate simulations suggest that climate of this region may become drier in summer and wetter in winter, which highlight the importance of hydrological and agricultural planning in Hungary. [Copyright &y& Elsevier]

A high resolution atmospheric modelling study was done for a 20-year recent historical period. The dynamic downscaling approach adopted used the Max Planck Institute Earth System Model (MPI-ESM) to drive the WRF running in climate mode. Three online nested domains were used covering part of the North Atlantic and Europe, with a resolution 81 km, and reaching 9 km in the innermost domain which covers the Iberian Peninsula. This paper presents the validation of the WRF configuration, which is based on historic simulations between 1986 and 2005 and observational datasets of near surface temperature and precipitation for the same period. The validation was done in terms of comparison of probability distributions between model results and observations, as daily climatologies, spatially averaged inside subdomains obtained with cluster analysis of the observations, for each of the four seasons. In addition, Taylor diagrams are presented for each of the seasons and subdomains. This validation approach was repeated with the results of a new WRF simulation with the same parameterisations but forced by the ERA-Interim reanalysis. The capacity of the MPI-ESM driven WRF configuration to compare with observations and in a manner similar to the ERA-Interim driven WRF, ensures the capacity of the configuration for climate and climate change studies. Considering the difficulty to simulate extremes in long term simulations, the results showed a comfortable comparison of both models (forced by climate model and reanalysis results) with observations. This provides us confidence on the continuity of using the MPI-ESM driven WRF configuration for climate studies. [ABSTRACT FROM AUTHOR]

This paper evaluates the risk of a water crisis – a substantial, sudden reduction in water supply – in the Monterrey Metropolitan Area (MMA), posed by climate threats and the vulnerability of its water supply system. Our analysis of long-term precipitation, water supply and water availability data reveals that the MMA is highly vulnerable to recurring periods of exceptionally low precipitation and scarce surface water availability. We identify two episodes in the recent past (1998 and 2013) when the MMA water supply system almost collapsed as reservoirs neared depletion in the face of abnormally dry weather. Furthermore our climate projections point to warmer and drier future conditions for the region and consequently, heightened climate threats. We conclude that the risk of a water crisis in the MMA is substantial and probably will increase due to climate change. This establishes a clear and pressing need for a comprehensive package of adaptation measures to mitigate the consequences of a water crisis should one occur as well as to reduce the likelihood of such an event. [ABSTRACT FROM AUTHOR]

Abstract: Agricultural water scarcity in the predominantly rainfed agricultural system of sub-Saharan Africa (SSA) is more related to the variability of rainfall and excessive non-productive losses, than the total annual precipitation in the growing season. Less than 15% of the terrestrial precipitation takes the form of productive ‘green’ transpiration. Hence, rainwater harvesting and management (RWHM) technologies hold a significant potential for improving rainwater-use efficiency and sustaining rainfed agriculture in the region. This paper outlines the various RWHM techniques being practiced in SSA, and reviews recent research results on the performance of selected practices. So far, micro-catchment and in situ rainwater harvesting techniques are more common than rainwater irrigation techniques from macro-catchment systems. Depending on rainfall patterns and local soil characteristics, appropriate application of in situ and micro-catchment techniques could improve the soil water content of the rooting zone by up to 30%. Up to sixfold crop yields have been obtained through combinations of rainwater harvesting and fertiliser use, as compared to traditional practices. Supplemental irrigation of rainfed agriculture through rainwater harvesting not only reduces the risk of total crop failure due to dry spells, but also substantially improves water and crop productivity. Depending on the type of crop and the seasonal rainfall pattern, the application of RWHM techniques makes net profits more possible, compared to the meagre profit or net loss of existing systems. Implementation of rainwater harvesting may allow cereal-based smallholder farmers to shift to diversified crops, hence improving household food security, dietary status, and economic return. The much needed green revolution and adaptations to climate change in SSA should blend rainwater harvesting ideals with agronomic principles. More efforts are needed to improve the indigenous practices, and to disseminate best practices on a wider scale. [Copyright &y& Elsevier]

Abstract: This paper shows that maximum snow depth and the length of accumulation and ablation periods observed at the local scale of Hornsund, SW Spitsbergen, are partly explained by monthly and seasonal values of the AO and NAO indices in the given and previous hydrological years. This analysis is followed by an application of a statistically efficient lumped parameter time series approach to modelling the dynamics of snow depth, based on daily meteorological and snow depth measurements from the same area. A dynamic Stochastic Transfer Function (STF) model is developed that follows the Data Based Mechanistic approach, where a stochastic data-based identification of model structure and an estimation of its parameters are followed by a physical interpretation. Apart from snow depth estimates, the model provides also the uncertainty limits. An analysis of the variation in parameter estimates over the whole measurement period provides an insight into the possible influence of recent climate change on snow cover dynamics at Hornsund. To help explain the physical meaning of the model parameters, we classified the data into accumulation and ablation periods. The models were run for each period separately. The first order model structure was found to be the most suitable to explain the variability of the snow cover. The cross-validation of models performance on the other years shows that the predictive value of the obtained models is not very consistent, with a mixture of good and bad years. The analysis shows that variability in the NAO and AO indices, reflecting the changes in global circulation patterns, is reproduced by local, physically meaningful, STF model-derived parameters in the form of residence times and temperature and precipitation related gains. [Copyright &y& Elsevier]

Abstract: This paper illustrates the ability of a set of different atmospheric circulation classifications from the COST733 Action “Harmonisation and Applications of Weather Types Classifications for European Regions” to describe the variability of winter precipitation over different climatic regions of Spain for the period 1961–1990. A Principal Component Analysis was first applied to identify the three regions (Atlantic, Mediterranean and Northern) with similar precipitation climatology. Different metrics such as the explained variation (EV), Pseudo-F index (PF) and the standard deviation (STD) have been used to evaluate the discriminatory power of the circulation classifications. A ranking of circulation classifications has been established for each region and for each metric. In the Atlantic and Northern regions, classifications that show a better performance correspond to the same type of algorithms, i.e. derived types with non-hierarchical cluster analysis. Instead, in the Mediterranean region, classifications using pre-defined types based on thresholds perform better. The classifications with the worst performance in every region belong to the subjective type. An analysis of the impact of the number of CTs on the discrimination ability of the classifications has also been carried out. Depending on the metric used, a different sensitivity of the classifications to the number of CTs has been found. The EV index shows an improvement when the number of CTs increases. Instead, the PF and the STD metrics showed a negative impact with an increasing number of CTs. [Copyright &y& Elsevier]

Abstract: This paper describes a weather radar siting procedure for a mountainous region in Greece using GIS. The established radar siting objectives consist of the detection and tracking of storms (rainstorms, hailstorms, and snowstorms) requiring operations at a low elevation angle as well as the detection of the vertical structure and evolution of a storm. Moreover, the objective includes precipitation intensity measurements and areal precipitation analysis, which is related to the incidence of permanent echoes and obstructions as well as to the maximum range achievable. Two types of siting criteria are employed; mainly strategic or regional criteria, and local criteria. The strategic criteria mainly consist of set back and communication considerations and local radar siting criteria include the area, geometry or morphology as well as local logistics and practical considerations. In this study, digitized maps of 1:100,000 scale with 100m contour interval are used. These digitized contour data are used to build the Digital Terrain Model (DTM, raster image) and produce the three-dimensional visualization of the area. The potential sites for the weather radar installation are identified on this three-dimensional DTM. The potential radar sites are located in complex mountainous areas, which results in additional selection difficulties. The selected site and its alternative fulfill the established purposes using the above-mentioned criteria. [Copyright &y& Elsevier]

Abstract: This paper shows an application of copulas to the probabilistic analysis of drought characteristics. Drought occurrences are analyzed by the Standardized Precipitation Index (SPI) computed on the mean areal precipitation, aggregated at 6months, observed in Sicily between 1921 and 2003. Assuming a drought period as a consecutive number of intervals where SPI values are less than −1, several characteristics are determined, namely: drought length, mean and minimum SPI values, and drought mean areal extent. Results of a preliminary analysis based on Kendall’s correlation and upper tail dependence coefficient, computed on observed and resampled data, show significant dependence properties between almost all the considered pairs. The four-dimensional joint distribution required to correctly model the stochastic structure of variables is determined by resorting to copula approach. This allows flexibility in choosing suitable marginals and dependence structure, and in simplifying the inference procedure as well. Drought return periods are then computed as mean interarrival time, taking into account two drought characteristics at a time by means of the corresponding bivariate marginals of the fitted four-dimensional distribution. Application of the proposed methodology to Sicilian precipitation series shows a good correspondence between empirical and theoretical joint return periods, thus indicating that copulas are adequate to jointly model drought characteristics and to compute exceedance probabilities of drought events. [Copyright &y& Elsevier]

Abstract: Human activity is known to have an important impact both in the radiation budget and the hydrological cycle. One particular aspect is the increase of anthropogenic aerosols due to changes in land use and industrial activity. However the relation between aerosols and precipitation is still far from being fully understood due to the complexity of the mechanisms involved and the lack of sound data. A multi-sensor approach, combining instruments meant to study aerosols and others meant at the study of precipitation, is required to get a better insight on this phenomenon. The International Research Centre for Telecommunications and Radar (IRCTR) has developed a meteorological radar called IDRA (IRCTR Drizzle Radar) aimed at obtaining high resolution temporal and spatial measurements of all sorts of precipitation including those non-detectable by standard meteorological radar like drizzle. The measurements obtained by the system, coupled with data obtained by other sensors placed in the Cabauw Experimental Site for Atmospheric Research (CESAR) observatory (Cabauw, The Netherlands), are expected to provide crucial information for a better characterization of these mechanisms. The information obtained can be used for a better spatial planning in order to reduce the impact of human activity in the climate. This paper describes the relevant characteristics of the system, its signal processing and the products obtained. [Copyright &y& Elsevier]

Abstract: In the last few years, remote sensing observations have become a useful tool for providing hydrological information, including the quantification of the main physical characteristics of the catchment, such as topography and land use, and of its variables, like soil moisture or snow cover. Moreover, satellite data have also been largely used in the framework of hydro-meteorological risk mitigation. Recently, an innovative Soil Wetness Variation Index (SWVI) has been proposed, using data acquired by the microwave radiometer AMSU (Advanced Microwave Sounding Unit) which flies aboard NOAA (National Oceanic and Atmospheric Administration) satellites. SWVI is based on a general approach for multi-temporal satellite data analysis (RAT – Robust AVHRR Techniques). This approach exploits the analysis of long-term multi-temporal satellite records in order to obtain a former characterization of the measured signal, in term of expected value and natural variability, providing a further identification of signal anomalies by an automatic, unsupervised change-detection step. Such an approach has already demonstrated, in several studies carried out on extreme flooding events which occurred in Europe in the past few years, its capability in reducing spurious effects generated by natural/observational noise. In this paper, the proposed approach is applied to the analysis of the flooding event which occurred in Europe (primarily in NW Spain) in June 2000. Results obtained, in terms of reliability as well as efficiency in space–time monitoring of soil wetness variation, are presented. Future prospects, in terms of exportability of the methodology on the new dedicated satellite missions, like ESA-SMOS and NASA-HYDROS, are also discussed. [Copyright &y& Elsevier]

Abstract: The enhanced greenhouse gas effect is expected to cause high temperature increase globally (1.0–3.5°C) and this will lead to an increase in precipitation in some regions while other regions will experience reduced precipitation (±20%). The impact of expected climate change will affect almost all aspects of human endeavour. The major focus of this paper is management of water resources under climate change for peace and prosperity in Swaziland. The impact of climate change on hydrology and water resources has been evaluated using general circulation model (GCM) results (rainfall, potential evapotranspiration, air temperature, etc.) as inputs to a rainfall runoff model. The evaluation of the effect of climate change on hydrology and water resources in Swaziland has been carried out in three catchments namely: Mbuluzi, Komati and Ngwavuma. MAGICC model was used to simulate the climate parameters for Swaziland given the baseline conditions. Eleven GCMs were evaluated and three of them were found to simulate very well the observed precipitation for Swaziland. These GCMs are: the Geophysical Fluid Dynamics Laboratory (GFDL), the United Kingdom Transient Resalient (UKTR) and the Canadian Climate Change Equilibrium (CCC-EQ). The three GCMs were used to project the temperature and precipitation changes for Swaziland for year 2075. This information was used to generate the temperature, precipitation and potential evapotranspiration values for the three catchments for year 2075. This information was used as input data to a calibrated WatBall rainfall runoff model. Simulation results (after taking into consideration water use projections) show a water deficit from June to September in both the Komati and Ngwavuma catchments and a water deficit from May to September in the Mbuluzi catchment. Efficient water utilization in the agricultural sector (i.e., using drip irrigation) gives a water savings of 33.6×106 m3per year (1.065m3/s), 47.6×106 m3per year (1.509m3/s) and 16.8×106 m3 per year (0.533m3/s) in the Komati, Mbuluzi and Ngwavuma catchments, respectively. The saved water could be used for other economic activities and meeting Swaziland’s water release obligations to downstream riparian states of South Africa and Mozambique. [Copyright &y& Elsevier]

The enhanced greenhouse gas effect is expected to cause high temperature increase globally (1–3.5°C) and this will lead to an increase in precipitation in some regions while other regions will experience reduced precipitation (±20%). The impact of expected climate change will affect almost all the sectors of the human endeavor. However, the major purpose of this paper is to evaluate the impact of climate change on hydrology and water resources for Swaziland. The impact of climate change on hydrology and water resources has been evaluated using General Circulation Model results (rainfall, potential evapotranspiration, air temperature etc.) as inputs to a rainfall runoff model. The evaluation of the effect of climate change on hydrology and water resources in Swaziland has been carried out in three catchments namely: Mbuluzi, Komati and Ngwavuma.The missing rainfall data in the original raw data files was estimated using regression analysis from the long-term daily averages rearranged in columns. Pairs of stations were analyzed to establish the ones that correlate the best in terms of the r2. Based on the relationship established in each pair, the linear formulae were applied on the larger original data files to estimate and fill the missing data gaps. The gaps in stream flow series were filled in using rainfall-runoff modeling technique.MAGICC-model has been used to simulate the climate parameters for Swaziland given the baseline conditions. Eleven GCMs were used and three of them were found to simulate very well the observed precipitation for Swaziland. These GCMs are: the Geophysical Fluid Dynamics Laboratory (GFDL), the United Kingdom Transient Resalient (UKTR), and the Canadian Climate Change Equilibrium (CCC-EQ). The three GCMs were used to project the temperature and precipitation changes for Swaziland for year 2075. This information was used to generate the temperature, precipitation and potential evapotranspiration values for the three catchments for year 2075. This information was used as input data to a calibrated WatBall rainfall runoff model. Simulation results show that there will be an annual runoff change of ±5% in the Komati catchment and ±2% in the Mbuluzi catchment given climate change conditions. Simulation results show a negative annual runoff change ranging from 4% to 23% in the Ngwavuma catchment under climate change scenarios. [Copyright &y& Elsevier]